System and method for communicating over mesh networks using waveform-enhanced, link-state routing

ABSTRACT

A communication system includes a plurality of mobile nodes forming a mesh network. A plurality of wireless communication links connect the mobile nodes together. Each mobile node is formed as a communications device and operative for transmitting data packets wirelessly to other mobile nodes via the wireless communications link from a source mobile node through intermediate neighboring mobile nodes to a destination mobile node using a link state routing protocol and multiple waveforms.

FIELD OF THE INVENTION

The present invention relates to the field of communications, and moreparticularly, to communications over mesh networks.

BACKGROUND OF THE INVENTION

Mesh networking routes data, voice and instructions between nodes andallows for continuous connections and reconfiguration around blockedpaths by “hopping” from one node to another node until a successfulconnection is established. Even if a node collapses, or a connection isbad, the mesh network still operates whether the network is wireless,wired and software interacted. This allows an inexpensive peer networknode to supply back haul services to other nodes in the same network andextend the mesh network by sharing access to a higher cost networkinfrastructure.

Wireless mesh networking is implemented over a wireless local areanetwork using wireless nodes. This type of mesh network is decentralizedand often operates in an ad-hoc manner. The wireless nodes operate asrepeaters and transmit data from nearby wireless nodes to other peers,forming a mesh network that can span large distances. In ad-hocnetworking, neighbors find another route when a node is dropped. Nodescan be either fixed or mobile, with mobile devices forming a mobilead-hoc network (MANET) known to those skilled in the art.

The mesh networks use dynamic routing capabilities. A routing algorithmensures that data takes an appropriate and typically the shortest routeto a destination. Some mobile mesh networks could include multiple fixedbase stations with “cut through” high bandwidth terrestrial linksoperating as gateways to fixed base stations or other services,including the Internet. It is possible to extend the mesh network withonly a minimal base station infrastructure. There are also manydifferent types of routing protocols that can be used in a mesh network,for example, an Ad-hoc On-Demand Distance Vector (AODV), Dynamic SourceRouting (DSR), Optimized Link State Routing protocol (OLSR) andTemporally-Ordered Routing Algorithm (TORR), as non-limiting examples.An example of a MANET using the OLSR protocol is disclosed in commonlyassigned U.S. Pat. No. 7,027,409, the disclosure which is herebyincorporated by reference in its entirety.

A multi-hop, ad-hoc wireless data communications network transmits apacket among different intermediate nodes using multiple hops as ittraverses the network from a source node to a destination node. In aTDMA mesh network, the channel time slot can be allocated before thenode data is transmitted. The channel transmit time is typicallyallocated in a recurring slot. The channel time typically is segmentedinto blocks as an epoch and blocks are divided into slots used by nodesto transmit data. If the data is an isochronous stream, the data can berepeatedly generated and presented at the source node for delivery to adestination node. The data is time dependent and is delivered by aspecified time.

OLSR is described in Request for Comment (RFC) 3626 by the InternetSociety Network working group, the disclosure which is incorporated byreference in its entirety. OLSR is a protocol for a mobile ad-hocnetwork (MANET) that optimizes a classical link state algorithm for amobile wireless LAN. It uses multipoint relays (MPR) to forward messagesbroadcast during a flooding process to reduce message overhead, ascompared to a classical flooding mechanism, where every node retransmitseach message when it receives the first copy of the message. The linkstate information is generated only by those nodes selected as amultipoint relay. Another optimization can be acquired by minimizing thenumber of control messages flooded in a network. Optimization can alsooccur when a MPR node discloses only links between itself and its MPRselectors. Thus, partial link state information can be distributedthroughout the network and used for route calculation. Optimal routes interms of the number of hops can be provided and are suitable for largeand dense networks.

OLSR is table driven and exchanges topology information with other nodesregularly. The MPR are the nodes responsible for forwarding trafficdistributed to the entire network. Thus, the MPR can reduce the numberof required transmissions and operate as a more efficient mechanismthroughout the network. OLSR can work in a distributed manner and doesnot depend on a central control. Each node can send control messagesperiodically and there can be some message loss. There is also norequirement for a sequenced delivery of messages.

OLSR and other link-state routing algorithms typically assume a singlewaveform (also known as physical layers or PHY) is used during theirnetwork topology and route discovery process. Different waveforms canhave different ranges and potentially different data ratecharacteristics. It is possible that the network topology and routesdiscovered by the routing algorithms will be different when usingdifferent waveforms. That network topology and routes can vary withwaveform is a problem.

OLSR proactively computes connection topology and multi-hop routes in amobile, ad-hoc, wireless network by exchanging OTA message packetsbetween network nodes. HELLO messages are exchanged among each node'slocal 1-hop neighbors. This allows the sensing of 1-hop neighborhoodlink states and the discovery of 1- and 2-hop neighbors. OLSR requiresall links used for routing to be bidirectional. Topology control (TC)messages are flooded across a wireless network to disseminate theimportant parts of each node's neighborhood information (the MPRselector neighbors). OLSR is able to compute a network connectivitymodel and efficient routes from each node to any other node in thenetwork for both directed and broadcast traffic.

OLSR implicitly assumes all HELLO and topology control over-the-air(OTA) message packets are transmitted using a single waveform or a setof waveforms having identical range (i.e., transmission distance orreach), and therefore, identical connectivity characteristics. The RFC3626 OLSR standard is able to compute a coherent model of networkconnectivity.

When multiple waveforms having different range characteristics are usedto transfer data in the network, the OLSR routing mechanism breaks down.This occurs because, in general, each different waveform will result indifferent network connectivity, i.e., which nodes can receive aparticular node's transmissions when using that waveform. For example,if node X and node Y establish a link transmitting on waveforms A and Brespectively, those waveforms are an intrinsic characteristic of thelink. If node X sends a packet to node Y, but uses waveform C totransmit, the OLSR discovered link may not exist using waveform C,possibly due to range or interference differences between waveforms Aand C.

SUMMARY OF THE INVENTION

A communication system includes a plurality of mobile nodes forming amesh network. A plurality of wireless communication links connect themobile nodes together. Each mobile node is formed as a communicationsdevice and operative for transmitting data packets wirelessly to othermobile nodes via the wireless communications link from a source mobilenode through intermediate neighboring mobile nodes to a destinationmobile node using a link state routing protocol and multiple waveforms.

Each mobile node can use multiple link state routing processes operatingin parallel at a mobile node for each waveform. Separate HELLO andtopology control messages can be transmitted and received per waveform.

A network conductivity model can be built at each mobile node for eachwaveform. A routing table can then be built at each mobile node for eachwaveform. Finally, the per-waveform routing tables can be merged into asingle composite routing table based on routing criteria. These routingcriteria can include minimum number of hops, minimum end-to-end latency,maximum data throughput, congestion avoidance, minimum powerconsumption, minimum bandwidth consumed, maximum throughput and droppedpackets per route, among others.

Each mobile node can also use a single link state routing process forall waveforms by transmitting separate HELLO messages to 1-hop neighborsand flooding a separate set of topology control messages per waveform. Anetwork topology table at each node can segregate link state informationfor each 1-hop neighbor by waveform. The 1-hop neighbor conductivity canalso be predicted based on reception characteristics for a receivedpacket on a single waveform. The reception characteristics can be formedas a received signal-to-noise ratio or similar measures. The link staterouting protocol can be formed as an optimized link state routing (OLSR)protocol. Multiple waveforms can have different ranges.

A method aspect is also set forth.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention willbecome apparent from the detailed description of the invention whichfollows, when considered in light of the accompanying drawings in which:

FIG. 1 is a block diagram of an example of a communications system thatcan be modified for use with the present invention.

FIG. 2 is a graph showing the frequency use for a single TDMA meshnetwork.

FIG. 3 is a graph similar to FIG. 1, but showing the frequency useoverlap as “bandwidth scavenging” for two TDMA mesh networks, listed asNet 1 and Net 2.

FIG. 4 is another graph showing the frequency use overlap as “bandwidthscavenging” for three TDMA mesh networks listed as Net 1, Net 2, and Net3.

FIG. 5 is a chart showing non-express, Quality of Service (QOS) TDMAchannel allocation, and showing how a data packet can travel from asource node A to a destination node E when transmitted by nodes andcrossing the TDMA network.

FIG. 6 is a chart showing an express Quality of Service and End-to-EndLatency (ETEL).

FIG. 7 is a block diagram showing a format of a representative exampleof an OLSR packet.

FIG. 8 is a high-level sequence diagram showing a multipoint relayselection.

FIG. 9 is a high-level diagram showing an example of multipoint relayingfor MPR flooding.

FIG. 10 is a high-level flowchart illustrating a basic process used inwaveform-enhanced, link-state routing for a multiple OLSR processes inaccordance with a non-limiting example of the present invention.

FIG. 11 is a high-level flowchart illustrating a basic single OLSRprocess in accordance with a non-limiting example of the presentinvention.

FIG. 12 is a high-level flowchart illustrating a waveform connectivityinference process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Different embodiments will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsare shown. Many different forms can be set forth and describedembodiments should not be construed as limited to the embodiments setforth herein. Rather, these embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope to those skilled in the art.

OLSR uses HELLO messages that have a 1-hop neighbor exchange. The 1-hopneighbors and link states are sensed and 2-hop neighbors are discovered.Topology control (TC) messages flood the network. MPR selector node1-hop neighbors and the corresponding link states are disseminated. TheOLSR algorithm at each node computes the network connectivity model andbuilds a route table.

In accordance with a non-limiting example of the present invention, itis desirable to use multiple waveforms having different ranges tosupport sometimes-conflicting goals. The number of hops are minimized,as are end-to-end latency, power consumption and bandwidth use. Datathroughput and reliability are maximized. Standard link-state routingalgorithms typically assume all link-state sensing, such as transmissionof an over the air (OTA) packet, is performed using a single-rangewaveform. The typical OLSR algorithm does not handle multiple waveformranges.

In accordance with the non-limiting example of the present invention, aseparate OLSR process is run for each waveform. For example, separateHELLO and topology control messages can be used per waveform. Networkconnectivity models can be built for each waveform.

Each node builds a composite routing table from multiple OLSR processconnectivity models. Whatever criteria are deemed important areoptimized, including the number of hops, end-to-end latency, powerconsumption, bandwidth use, data throughput and reliability.Computational and bandwidth resources are consumed, but it isadvantageous.

A single OLSR process can be used per waveform. Each node can send, foreach waveform, a separate HELLO message containing 1-hop neighbors. Fromthis each receiving node can collect 1- and 2-hop neighborhoods and1-hop link states for each waveform. A separate topology control messagecan be flooded, per waveform, for the 1-hop MPR selector nodes and thecorresponding link states. Receiver nodes can build a network connectionmodel per waveform. Each node can then build a composite routing tableoptimizing criteria as indicated above.

One preferred solution uses a single OLSR process run in each node. Thisprocess can be modified to exchange a separate and independent set of1-hop neighbor HELLO messages for each waveform. The HELLO messagecontains only 1-hop neighborhood information for that waveform. Fromthis, each node can build a 2-hop neighborhood for each waveform. TheOLSR state table can be extended to segregate link state information foreach 1-hop neighbors by waveform. Further details are explained in thedescription.

Waveform connectivity inferences can be based upon a differentwaveform's measured link-state performance and connectivity. HELLOmessaging can be used as in standard OLSR using a single waveform totransmit the HELLO messages. The link's reception characteristics can becollected, such as the signal to noise ratio. Heuristics can then inferother waveforms' link-state performance and connectivity though theyhave not been directly measured. In this way 1-hop link states and 1-and 2-hop neighborhoods can be generated from a single waveform's HELLOmessaging. From each node a topology control message can be periodicallyflooded containing 1-hop MPR selector link state, either for allwaveforms or only a single waveform. Network connectivity can be builtper waveform and each node can then build a composite routing table.

It should be understood that by performing the inference at the node andcollecting the link-state data, it is possible to make a betterinference, but pay more in bandwidth to distribute the full set ofpartially synthesized link-state waveform data. By delaying anyperformance of the inference until after the measured link-state datahas been distributed, it is possible to save some bandwidth by notdistributing synthesized link-state data, but pay a potential cost ofperforming poor inference because it is not possible to use localfeedback on previously inferred link metrics/state to guide theinference.

Separate routing tables can be built for multiple different-range radiowaveforms and a single composite routing table can be built based onmultiple optimization criteria in an ad-hoc, multi-hop, mobile wirelessmesh network. For single OLSR processes and the waveform connectivityinferences, the system and method operates inchannel-bandwidth-efficient fashion.

The system and method is advantageous to build multi-waveform routingtables with little additional bandwidth usage to allow competitiveadvantages for mobile wireless mesh ad-hoc networks.

An example of a communications system that can be used and modified foruse with the present invention is now set forth with regard to FIG. 1.

An example of a radio that could be used with such system and method isa Falcon™ III radio manufactured and sold by Harris Corporation ofMelbourne, Fla. It should be understood that different radios can beused, including software defined radios that can be typicallyimplemented with relatively standard processor and hardware components.One particular class of software radio is the Joint Tactical Radio(JTR), which includes relatively standard radio and processing hardwarealong with any appropriate waveform software modules to implement thecommunication waveforms a radio will use. JTR radios also use operatingsystem software that conforms with the software communicationsarchitecture (SCA) specification (see www.jtrs.saalt.mil), which ishereby incorporated by reference in its entirety. The SCA is an openarchitecture framework that specifies how hardware and softwarecomponents are to interoperate so that different manufacturers anddevelopers can readily integrate the respective components into a singledevice.

The Joint Tactical Radio System (JTRS) Software Component Architecture(SCA) defines a set of interfaces and protocols, often based on theCommon Object Request Broker Architecture (CORBA), for implementing aSoftware Defined Radio (SDR). In part, JTRS and its SCA are used with afamily of software re-programmable radios. As such, the SCA is aspecific set of rules, methods, and design criteria for implementingsoftware re-programmable digital radios.

The JTRS SCA specification is published by the JTRS Joint Program Office(JPO). The JTRS SCA has been structured to provide for portability ofapplications software between different JTRS SCA implementations,leverage commercial standards to reduce development cost, reducedevelopment time of new waveforms through the ability to reuse designmodules, and build on evolving commercial frameworks and architectures.

The JTRS SCA is not a system specification, as it is intended to beimplementation independent, but a set of rules that constrain the designof systems to achieve desired JTRS objectives. The software framework ofthe JTRS SCA defines the Operating Environment (OE) and specifies theservices and interfaces that applications use from that environment. TheSCA OE comprises a Core Framework (CF), a CORBA middleware, and anOperating System (OS) based on the Portable Operating System Interface(POSIX) with associated board support packages. The JTRS SCA alsoprovides a building block structure (defined in the API Supplement) fordefining application programming interfaces (APIs) between applicationsoftware components.

The JTRS SCA Core Framework (CF) is an architectural concept definingthe essential, “core” set of open software Interfaces and Profiles thatprovide for the deployment, management, interconnection, andintercommunication of software application components in embedded,distributed-computing communication systems. Interfaces may be definedin the JTRS SCA Specification. However, developers may implement some ofthem, some may be implemented by non-core applications (i.e., waveforms,etc.), and some may be implemented by hardware device providers.

For purposes of description only, a brief description of an example of acommunications system that could incorporate optical link state routingas modified in accordance with a non-limiting example, is describedrelative to a non-limiting example shown in FIG. 1. This high-levelblock diagram of a communications system 50 includes a base stationsegment 52 and wireless message terminals that could be modified for usewith the present invention. The base station segment 52 includes a VHFradio 60 and HF radio 62 that communicate and transmit voice or dataover a wireless link to a VHF net 64 or HF net 66, each which include anumber of respective VHF radios 68 and HF radios 70, and personalcomputer workstations 72 connected to the radios 68,70. Ad-hoccommunication networks 73 are interoperative with the various componentsas illustrated. Thus, it should be understood that the HF or VHFnetworks include HF and VHF net segments that are infrastructure-lessand operative as the ad-hoc communications network. Although UHF radiosand net segments are not illustrated, these could be included.

The HF radio can include a demodulator circuit 62 a and appropriateconvolutional encoder circuit 62 b, block interleaves 62 c, datarandomizer circuit 62 d, data and framing circuit 62 e, modulationcircuit 62 f, matched filter circuit 62 g, block or symbol equalizercircuit 62 h with an appropriate clamping device, deinterleaver anddecoder circuit 62 i modem 62 j, and power adaptation circuit 62 k asnon-limiting examples. A vocoder circuit 62 l can incorporate the decodeand encode functions and a conversion unit which could be a combinationof the various circuits as described or a separate circuit. These andother circuits operate to perform any functions necessary for thepresent invention, as well as other functions suggested by those skilledin the art. Other illustrated radios, including all VHF mobile radiosand transmitting and receiving stations can have similar functionalcircuits.

The base station segment 52 includes a landline connection to a publicswitched telephone network (PSTN) 80, which connects to a PABX 82. Asatellite interface 84, such as a satellite ground station, connects tothe PABX 82, which connects to processors forming wireless gateways 86a, 86 b. These interconnect to the VHF radio 60 or HF radio 62,respectively. The processors are connected through a local area networkto the PABX 82 and e-mail clients 90. The radios include appropriatesignal generators and modulators.

An Ethernet/TCP-IP local area network could operate as a “radio” mailserver. E-mail messages could be sent over radio links and local airnetworks using STANAG-5066 as second-generation protocols/waveforms, thedisclosure which is hereby incorporated by reference in its entiretyand, of course, preferably with the third-generation interoperabilitystandard: STANAG-4538, the disclosure which is hereby incorporated byreference in its entirety. An interoperability standard FED-STD-1052,the disclosure which is hereby incorporated by reference in itsentirety, could be used with legacy wireless devices. Examples ofequipment that can be used in the present invention include differentwireless gateway and radios manufactured by Harris Corporation ofMelbourne, Fla. This equipment could include RF5800, 5022, 7210, 5710,5285 and PRC 117 and 138 series equipment and devices as non-limitingexamples.

These systems can be operable with RF-5710A high-frequency (HF) modemsand with the NATO standard known as STANAG 4539, the disclosure which ishereby incorporated by reference in its entirety, which provides fortransmission of long distance HF radio circuits at rates up to 9,600bps. In addition to modem technology, those systems can use wirelessemail products that use a suite of data-link protocols designed andperfected for stressed tactical channels, such as the STANAG 4538 orSTANAG 5066, the disclosures which are hereby incorporated by referencein their entirety. It is also possible to use a fixed, non-adaptive datarate as high as 19,200 bps with a radio set to ISB mode and an HF modemset to a fixed data rate. It is possible to use code combiningtechniques and ARQ.

There now follows a description of “bandwidth scavenging” followed by amore detailed explanation of the Quality of Service enhancements thataddress the end-to-end latency problems identified above. There thenfollows a description of the optimal link state routing as modified inaccordance with a non-limiting example of the present invention. Itshould be understood that many of the mesh networks operate using a TimeDivision Multiple Access (TDMA) protocol. Depending on the configurationof a TDMA mesh network, a large portion or even a majority of configuredbandwidth can be wasted. This can be true even when considering amaximum possible theoretical channel utilization.

TDMA mesh networks typically include a plurality of wireless nodes thatcommunicate with each other using primary and secondary frequencies andusing TDMA epochs that are divided into a beacon interval operative as anetwork control interval, sometimes a digital voice (DV) interval, and adigital data (DD) interval. For purposes of this description, TDMA meshnetworks use a slot of channel time that is allocated prior to a nodeactually transmitting data during the allocated slot. Details of how theTDMA channel allocation mechanism works is not described in detailbecause it is sufficient that some algorithm is used to allocate apotentially recurring slot of channel time in which a particular nodemay transmit the data.

TDMA channel time allocation algorithms typically segment channel timeinto blocks. Each block is an epoch. Blocks are subdivided into slotsused by nodes to transmit data. It is assumed that the data to betransmitted constitutes an isochronous stream, meaning that largeportions of data are repeatedly generated and presented at the sourcenode for delivery to the destination node. The data is typically timedependent, and must be delivered within certain time constraints.Multiple frequencies can be allocated to a single TDMA mesh networkusing a primary frequency and a plurality of secondary frequencies,sometimes up to four secondary frequencies in non-limiting examples.

As shown in FIG. 2 for a TDMA mesh network, only the digital datainterval actually uses some of the secondary frequencies. All secondaryfrequencies during the beacon and digital voice intervals are unused.These unused portions of allocated frequencies can be referred to aswasted channel time, or more simply as channel wastage. Depending uponthe relative sizes of the beacon, digital voice and digital dataintervals, and how many secondary frequencies are allocated, a majorityof allocated bandwidth can consist of channel wastage.

Of course, it is possible to configure TDMA mesh networks to minimizechannel wastage. For example, a TDMA mesh network could be configuredusing only the primary frequency and no secondary frequencies, resultingin no channel wastage. Whenever any secondary frequencies are allocated,however, channel wastage occurs. Even in this case channel wastage canbe minimized by maximizing the relative size of the digital datainterval at the expense of any beacon and digital voice interval sizes.Unfortunately, there are practical constraints limiting how much channelwastage can be limited.

Beacon interval size is typically dictated by the number of nodes in theTDMA mesh network, for example, typically wireless nodes and oftenmobile or fixed nodes, as in a mobile ad-hoc network (MANET). More nodesmean a larger beacon interval. Digital voice or video interval size isdictated by the expected peak requirement for simultaneous digital voiceand video services. These digital voice and video intervals can usuallybe reduced below an expected peak need at the cost of failing toprovision the peak need at the likely cost of the digital voice or videofailing to work exactly when it is most needed by the user in the field.

The solution to channel wastage is achieved by recognizing that a secondTDMA mesh network, for example, termed “Net 2” in FIG. 3, can use theunused TDMA portions of the first (“Net 1”) TDMA mesh network'ssecondary frequencies, for its secondary frequency digital data usage.In effect, the system can scavenge a part of the secondary frequencychannels unused by the first TDMA mesh network, thereby reducing channelwastage.

An example of the “bandwidth scavenging” as described is shown in FIG.3. For example, a sixth frequency, f6, is allocated and used as theprimary frequency for the second TDMA mesh network. Its start of epochis offset from the start of epoch for the first TDMA mesh network, suchthat the digital data secondary frequency TDMA usage for the second TDMAmesh network falls in the unused parts of the secondary frequency usagemap of the first TDMA mesh network. In this non-limiting example,channel wastage has been reduced by about 50%.

It should be understood that “bandwidth scavenging” as describedrequires several functions as follows:

1. Allocate a new, currently unused frequency for the second TDMA meshnetwork primary frequency;

2. Offset the start of epoch for the second TDMA mesh network from thestart of epoch for the first TDMA mesh network so that the secondaryfrequency usage of the second TDMA mesh network falls in the unusedportion of the secondary frequency usage map of the first TDMA meshnetwork; and

3. Maintain the start of epoch offsets during overlapping operation.

Allocating a new, currently unused frequency such as the primaryfrequency (number 1 above) can be done during the TDMA mesh network'sinitial configuration, or can be accomplished automatically via aconfiguration allowing automatic “bandwidth scavenging” in accordancewith non-limiting examples of the present invention.

Establishing the initial start of epoch offset (number 2 above) can beaccomplished with minimal steps. When a TDMA mesh network, e.g., thesecond TDMA mesh network, hears another mesh network, e.g., the firstTDMA mesh network, with which it wishes to perform bandwidth scavenging,those radios or wireless nodes for the second TDMA mesh network thathear the radios or wireless nodes in the first TDMA mesh network createan artificial, or “phantom” radio or node, whose start of epoch is atthe desired offset based upon the inferred start of epoch for the firstTDMA mesh network. This “phantom” node is included in the second TDMAmesh network node's network synchronization algorithm, i.e., epochsynchronization, beacon synchronization or smoothing algorithm. Theeffect of including this “phantom” node is to gradually andsystematically move the second TDMA mesh network's start of epoch to thedesired offset. Other algorithms to establish the initial start of epochoffset are also possible.

Maintaining a start of epoch offset after the offset was firstaccomplished (number 2 listed above) also takes minimal steps. The“phantom” nodes in the network synchronization algorithm can becontinued.

The “bandwidth scavenging” algorithm as described is flexible regardlessof the configuration of the overlapping TDMA mesh network. This isbecause during the beacon interval only the primary frequency can beused by a TDMA mesh network. Thus, the beacon interval portion of theTDMA mesh network's secondary frequency map is usually available for useby other TDMA mesh networks. As a result, the “bandwidth scavenging” asdescribed can be used, even when the overlapping TDMA mesh network'sdigital voice interval has been eliminated.

Extensions of this type of system are also possible. As part of itscoexistence configuration, a TDMA mesh network can be configured toshift automatically to “bandwidth scavenging” as described whenencountering another TDMA mesh network either to expand its effectivebandwidth or to conserve the overall used bandwidth.

Another extension is to use bandwidth scavenging to overlap more thantwo TDMA mesh networks. An example of this for three TDMA mesh networksis shown in FIG. 4, which shows a chart similar to FIG. 3, but nowshowing a third TDMA mesh network, “Net 3,” which is overlapped byallocating its primary frequency, f7, and aligning this third TDMA meshnetwork's start of epoch to allow its digital data secondary frequencyusage to overlap or fall within the unused portions of the first andsecond TDMA mesh network's secondary frequency usage maps.

In some examples, the available unused secondary frequency gaps are toosmall to fit the alternate third TDMA mesh network's digital datainterval. This is not a serious drawback, and possible alternativemechanisms can handle this situation.

“Bandwidth scavenging” as described is relevant to many REcommunications devices. Multiple secondary frequencies can be used toextend total radio or wireless node bandwidth, and use the secondaryfrequencies during a digital data interval. As a result, thesefrequencies are wasted during digital voice, digital video, and duringbeacon intervals. “Bandwidth scavenging” as described allows any wastedparts of the secondary frequencies to be used when multiple TDMA meshnetworks are present.

A TDMA type scheme can also be applied in a coarse-grained fashion to aTDMA mesh network radio frequency versus time usage characteristics toallow these TDMA mesh networks to “scavenge” the unused parts of eachother's secondary frequencies, by offsetting in time each TDMA meshnetwork's secondary frequency usage with respect to the other(s).Bandwidth scavenging can be used in TDMA mesh networks to accomplishreuse of the otherwise wasted parts of wireless nodes or radio'ssecondary frequencies.

It should be understood that a TDMA mesh network architecture can beformed of different types, and a TDMA epoch in a non-limiting example asset forth comprises a network control interval as a beacon interval anddigital data interval. A network control interval as a plurality ofbeacons uses only the primary frequency. The digital data interval usesboth the primary and secondary frequencies via the TDMA channelallocation.

It is possible to reduce the requirements that any secondary frequencyusage interdigitates, i.e., be non-overlapping. It should be understoodthat multiple TDMA mesh networks should be synchronized. Non-overlappingof secondary frequency usage, while desirable and optimal, is notstrictly required. Thus, non-overlapping secondary frequency usage couldbe shown as an example of a more general inter-meshing networksynchronization.

A “phantom node” synchronization algorithm can allow synchronizationbetween and among multiple mobile, ad-hoc, and TDMA mesh networks.Moreover, there are several ways “bandwidth scavenging” could accomplishinter-network synchronization. Phantom node synchronization is just one.

A “phantom node” synchronization algorithm achieves and maintainssynchronization between and among multiple mobile, ad-hoc, mesh networksindependent from “bandwidth scavenging” as described above in accordancewith non-limiting examples of the present invention. As such, this typeof “phantom node” synchronization algorithm can be useful not just for“bandwidth scavenging” inter-meshed TDMA mesh network synchronization,but also useful when multiple mesh networks should be synchronized forother reasons, e.g., to simplify the job of gateway nodes or simplifythe coexistence and interoperability of multiple TDMA mesh networks onthe same frequency in the same place.

One non-limiting example is a gateway between two high performance TDMAmesh networks that typically communicates using a TDMA epoch that has abeacon interval, digital voice interval, and digital data interval. Thegateway node could be a member of both TDMA mesh networks. The gatewaynode should transmit two beacons, one for each of the two TDMA meshnetworks. If the two TDMA mesh networks are not synchronized, however,problems could arise. For example, sometimes the beacon transmit timesfor the two beacon transmissions will overlap. Because it isunattractive cost-wise to include two independent radios in the gatewaynode, typically a wireless node, the gateway node will be able totransmit one of the two beacons. Moreover, even if the gateway did havetwo independent radios in the one node, when both TDMA mesh networks areoperating on the same frequency, only a single beacon would betransmitted at a time. Otherwise, a collision would occur with theresult that no node would correctly receive either beacon. With the twooverlapping TDMA mesh networks having the same epoch duration, or aninteger multiple thereof, it could be synchronized for simplifying thegateway node's operation. This inter-network gateway functionality is anexample of interoperability.

Coexistence is another example when the system might want to synchronizethe operation of multiple TDMA mesh networks. It is desirable for thebeacon interval of each TDMA mesh network to fall within the digitaldata interval, and in some networks, the digital voice and/or digitaldata interval of the co-located TDMA mesh networks, so that each TDMAmesh network's beacon transmissions would not collide with those of theother TDMA mesh networks. A TDMA mesh network could make an artificialreservation during a digital data interval corresponding to the otherTDMA mesh networks beacon interval. As a result, two TDMA mesh networksprevent any of their nodes from making digital data transmissions orbeacon transmissions that would collide with the other TDMA meshnetworks' beacon transmissions. For a TDMA mesh network to continue tofunction reliably and robustly, many of its beacon transmissions must becorrectly received by neighboring nodes in the TDMA mesh network. Inthis case, synchronization is needed such that these “artificial” TDMAchannel reservations are stationary with respect to the other TDMA meshnetworks' beacon intervals.

“Phantom node synchronization” is a simple and robust technique toachieve synchronization and maintain synchronization between potentiallymultiple TDMA mesh networks, completely independent of the reasons whythe synchronization is desired.

The problem of minimizing end-to-end latency can also be addressed. Inthis description, quality of service can typify the deliver of real-timedata and the problem of minimizing end-to-end latency is addressed,particularly in a multi-hop ad-hoc wireless network. It should beunderstood that the time taken by over-the-air (OTA) headers,inter-frame spaces, cyclic redundancy checks (CRC), trailers, stuffbits, and the like are typically treated as part of the OTA transmissiontime.

Quality of Service (QoS) parameters are optimized when deliveringreal-time data across a data communications network, and typicallyinclude end-to-end latency, jitter, throughput and reliability. Thedescription as follows focuses on end-to-end latency.

End-to-end latency can be defined as the time it takes to deliver a datapacket from a source node to a destination node. End-to-end latency canalso be defined as the time duration from when the data packet ispresented to the data communications layer of the stack at the sourcenode, to when the data packet is passed up from the data communicationlayer of the stack at the destination node. End-to-end jitter can bedefined as the variance of end-to-end latency, sometimes expressed asthe standard deviation of latency.

In a multi-hop, ad-hoc, wireless data communications network, a packetwill, in general, be transmitted multiple times, i.e., take multiplehops, as it traverses the network from the source node to thedestination node. For purposes of this description, TDMA mesh networksuse a slot of channel time that is allocated prior to a node actuallytransmitting data during the allocated slot. Details of how the TDMAchannel allocation mechanism works are not described in detail becauseit is sufficient that some algorithm is used to allocate a recurringslot of channel time in which a particular node may transmit the data.TDMA channel time allocation algorithms typically segment channel timeinto blocks. Each block is an epoch. Blocks are subdivided into slotsused by nodes to transmit data. It is assumed that the data to betransmitted constitutes an isochronous stream, meaning that largeportions of data are repeatedly generated and presented at the sourcenode for delivery to the destination node. The data is typically timedependent, and must be delivered within certain time constraints.

When a data packet traverses the TDMA mesh network from a source node toa destination node, it will be transmitted by some sequence of nodes.For example, this sequence consists of nodes A, B, C, and D todestination node E, where node A is the source node. For examplepurposes, the system assumes each transmitted data packet issuccessfully received by each hop's destination node.

FIG. 5 is a timing chart illustrating how a particular data packet maytravel from source node A to destination node E when transmitted by eachnode crossing the TDMA mesh network based upon a non-express-QoS(Quality of Service) TDMA channel allocation algorithm. Each nodecarrying the isochronous data stream across the TDMA mesh network hasbeen granted a slot by the TDMA algorithm that repeats in each TDMAepoch. During TDMA epoch N, source node A transmits the data packet tonode B during the first TDMA epoch. Next, during TDMA epoch N+1, node Btransmits the data packet to node C, and node C transmits it to node D.Finally, during TDMA epoch N+2, node D transmits the data packet to nodeE, the final destination. The end-to-end over-the-air (OTA) latency forthe data packet's traversal is just under two TDMA epochs. OTA latencyincludes neither stack processing time, the time to travel up/down thestack within the source and destination nodes, nor the time the datapacket waits in the queue at the source node for arrival of the sourcenode's allocated transmission time, which is shown as the first ‘A’channel time allocation in TDMA epoch N in FIGS. 5 and 6.

The bold-lined portions in FIGS. 5 and 6 represent data packetstransmitted over-the-air (OTA). No data packet is transmitted in “theslot” for node E. The slot is present to show that node E exists. Itcould be considered an “imaginary” slot. This is where node E maytransmit if it were to transmit an OTA data packet if it were not adestination node. Because node E can be a distraction node, it onlyreceives packets in this example and never transmits a data packet.

The system analyzes hop latencies that fit together along the routetraversed, with the express Quality of Service (QoS) algorithm asdescribed to reduce end-to-end latency. End-to-end OTA route traversallatency can be substantially reduced by modifying the TDMA channel timeallocation algorithm to order the transmission allocation to each nodeparticipating in the data stream's route within each TDMA epoch as shownin FIG. 6.

Minimum end-to-end latency can be achieved when the next-hop's TxOp(transmission opportunity) for the data stream whose latency the systemis trying to minimize occurs as soon as possible after the QoS datapacket to be relayed is received, ideally at the data slot followingreception. When viewed as a sequence of TxOps, the optimal QoS TxOpsequence consists of a series of adjacent time-sequential TxOps in theepoch, from the source node to destination node, one TxOp for each hop.By paying attention to how hop latencies fit together, and thenoptimally ordering the resulting sequence of channel time allocationswithin the epoch, the end-to-end latency shown in FIG. 6 is reduced toless than half an epoch.

To achieve minimal OTA end-to-end latency, the Express QoS allocationalgorithm can order each node's recurring transmission time within theepoch in route-traversal sequence, i.e., sequentially in the epoch datainterval from a source node to a destination node. This provides themajority of end-to-end OTA latency reduction.

In addition, the Express QoS allocation algorithm can place eachallocation in the route sequence as close as possible to its neighboringallocations in the route sequence. Though not as important as theordering of allocated slots, this provides some additional reduction inend-to-end OTA latency and allows longer routes to fit within singleepoch.

For Express QoS to be able to reduce end-to-end latency, sufficientchannel time, i.e., slots, should be available and unallocated such thatExpress QoS has a choice of allocations at multiple nodes along theroute. The more slot choices Express QoS has available, the more it canminimize end-to-end latency.

The Express QoS allocation algorithm can coordinate local node channeltime allocation across the spatial extent of the source-to-destinationtraversal route. This requires some inter-node communication. Typically,communication between adjacent nodes is required and communicationbeyond adjacent neighbors along the route is not required.

It should be understood that full duplex operation in wireless TDMA meshnetworks is typically achieved by creating two data streams, one streamfor each direction of travel. Express QoS as described requires adifferent ordering of channel allocations for each direction, since anoptimal slot allocation sequence in one direction will be a worst-caseallocation for the opposite direction.

Express QoS as described can substantially reduce the latencyexperienced by packets belonging to a QoS data stream flowing across awireless TDMA “multi-hop” mesh network. This improved QoS latency asdescribed is applicable to demanding QoS-sensitive applications, such astwo-way real-time voice.

To quantify and characterize the latency improvement that can beexpected, consider the expected latency of a packet traveling across awireless TDMA mesh network of diameter “D” from one edge of the networkto the opposite edge. In all cases at each hop the placement of thetransmission slot within the TDMA epoch's digital data interval isentirely dependent upon the details of the operation of the TDMA channelallocation algorithm. Many algorithms are possible. Unless the algorithmexplicitly optimizes relative slot positions along the route so as tominimize the latency experienced by packets traversing that route,however, there is no reason to expect the data packets will achieve an“average” per-hop traversal latency of less than the approximate 0.5TDMA epochs expected by random slot placement. Using the Express QoSTDMA channel allocation algorithm as described, however, per-hoptraversal latency as low as the OTA data transmission time can beachieved provided all allocation can be fit within a single epoch. Asshown in FIG. 6, using Express QoS as described, a data packet cantraverse the entire route in less than a single epoch.

Express QOS is an extension of the TDMA channel allocation algorithm tominimize end-to-end latency along a route across a multi-hop TDMA meshnetwork, adding a latency-minimizing extension to the TDMA algorithm.

There are other possible extensions. For example, when nodes move,established pre-existing routes can change. Because the express QOS TDMAchannel time allocations are route-dependent, when nodes move and routeschange, the express QOS channel time allocation algorithm/mechanism mustrevisit and refigure-out what is the best, i.e., the lowest latency,allocations and make changes in the pre-existing allocationsaccordingly. This refiguring-out could be triggered by detecting changesin a route or be accomplished periodically with the re-do frequencybased on a metric for how rapidly the relevant parts or overall networktypology changes.

It is also possible to consider what happens when a new express QOSallocation request is made while previous requests are still active.When this happens, it is likely to be beneficial to revisit previouslygranted request, i.e., the allocations previously made, in order tooptimize the efficiency of the allocations considered as a whole, i.e.,minimize the latency across all active express quality of servicestreams, both old and new.

In accordance with the non-limiting example of the present invention,the network topology and route discovery routing algorithms acrossmultiple waveforms can have different ranges and potentially differentdata rates and characteristics.

For purposes of description, an analysis of the OLSR protocol is firstdescribed followed by details of the system and method in accordancewith non-limiting aspects of the present invention.

OLSR is a protocol that connects mobile ad-hoc networks (MANETs) alsotermed wireless mesh networks. It is a link-state routing protocol thatcalculates a optimized routing table based upon collected data aboutavailable connectivity. OLSR uses HELLO messages to find a node's 1-hopand its 2-hop neighbors through responses from 1-hop neighbors. A nodecan select MPR (Multi-Point Relay) based on the 1-hop nodes that offersuperior coverage of its 2-hop neighbors. Each node can have amultipoint relay selector set consisting of its 1-hop neighbors thathave selected it as their MPR. MPR efficiently forward broadcastmessages during the flooding process, thus reducing flooding overhead.Link-state information is flooded by those nodes elected as MPR. OLSR isa table driven protocol that exchanges topology information with othernodes on the network regularly. In an OLSR system, a node is typically aMANET router that implements the OLSR routing protocol. An OLSRinterface is typically a network device that participates in a MANETrunning OLSR. One node can have several OLSR interfaces with eachassigned a unique IP address. A non-OLSR interface could be a networkdevice not participating in a MANET running OLSR. A single OLSRinterface node could be a node that has a single OLSR interfaceparticipating in an OLSR routing domain. A multiple OLSR interface nodecould be a node having multiple OLSR interfaces.

A node can have a main address as an “originator address” of messagesemitted by the node. For example, the node X could be a neighbor node ofnode Y, if node Y can hear node X such as when a link exists between anOLSR interface on node X and an OLSR interface on node Y. A node heardby a neighbor can be a 2-hop neighbor. A multipoint relay (MPR) could bethe node that is selected by its 1-hop neighbor, node X, to “retransmit”the broadcast messages as long as the message is not a duplicate. Amultipoint relay selector could be the node that selected its 1-hopneighbor as multipoint relay. A link could be a pair of OLSR interfacesfrom two different nodes that are susceptible to hear each other. Asymmetric link could be a bidirectional link between two OLSR interfacesand an asymmetric link could be a link between two OLSR interfacesverified in one direction. A symmetric 1-hop neighborhood of any node Xis a set of nodes having at least one symmetric link to X. A symmetric2-hop neighborhood would be the 2-hop neighborhood of X that excludes Xitself.

OLSR is suited to large and dense mobile networks using hop-by-hoprouting such that each node uses its local information to route packets.

OSLR can minimize the overhead from flooding of control traffic by usingonly MPR to retransmit control messages. This reduces the number ofretransmissions required to flood a message to all nodes in the network.A partial link state would only be required to be flooded to provide ashortest path route. OLSR works in a distributed manner and each nodecan send control messages periodically and sustain some loss ofmessages. There is no requirement for sequenced delivery of messages.Each control message can contain a sequence number that is incrementedfor each message. Thus, a recipient of a control message can identifythat information that is more recent, even if some messages have beenreordered in transmission. There is some support for a sleep modeoperation and multicast-routing for different protocol extensions.

Multipoint relays can minimize the overhead of flooding messages byreducing redundant transmissions. Each node would select a set of nodesin its symmetric 1-hop neighborhood to retransmit the messages. Thus,the selected neighbor nodes can be termed the “multipoint relay” (MPR)set of the node.

Referring now to FIGS. 7-9, there follows a basic description of theOLSR algorithm. It should be understood that OLSR is a pro-activerouting protocol such that routes can be set up based on continuouscontrol traffic and all routes can be maintained all the time. The OLSRprotocol can have neighbor/link sensing, optimized flooding andforwarding with multipoint relaying and link-state messaging and routecalculation.

FIG. 7 is a block diagram of an example of an OLSR packet format shownat 100. The OLSR header 102 includes a packet length indicator 104 andpacket sequence number 106 followed by a message portion 108 that wouldinclude a message type indicator 110, VTIME 112, message size 114,originator address 116, a Time to Live data 118, hop count 120 andmessage sequence number 122 followed by the message 124.

The neighbors and links are detected by HELLO messages and all nodes cantransmit HELLO messages on a given interval. The HELLO could beasymmetric and symmetric. Multipoint relaying is used to reduce thenumber of duplicate retransmissions while forwarding a flooded packet.Multipoint relaying restricts the set of nodes retransmitting a packetfor flooding to a subset of all nodes. The size of the subset depends onthe topology of the network.

FIG. B shows a multipoint relay sequence at 130 in which nodes canselect and maintain an MPR. The MPR labeled X for a 2-hop neighbor Y issuch that Y can be contacted via X. The nodes register and maintain MPRselectors, and if an OLSR packet is received from an MPR selector,messages contained in that packet are forwarded for known and unknownmessage types if TTL is greater than zero. FIG. 9 shows an example offlooding with multipoint relaying with different nodes shown by thecircles indicated with the letter “n”.

OLSR can have a modular design with a scheduler that runs in the thread.An OLSR daemon can include a socket parser with registered sockets andan OLSR packet parser that has parse functions. The different tables areinformation repositories and can include duplicate tables with ascheduler. It is possible to have plug-ins as dynamically loadedlibraries (DLLS) as code that can be linked and loaded. OLSR MPRflooding can be used for net-wide broadcasts.

OLSR's network connectivity, topology and route computations can beextended to handle multiple waveforms having different ranges andpotentially different data rates.

It is possible to use multiple OLSR processes. OLSR can be adapted tohandle multiple waveforms having different radio ranges. This can beaccomplished by running a separate OLSR process in each node for each ofthe waveforms. Each OLSR process performs its own independent set ofHELLO and Transmit Control (TC) message transmissions using a differentwaveform. Each OLSR process builds a model of network connectivity,based on its waveform's range, in the usual OLSR fashion. Then each OLSRprocess constructs a routing table for its waveform's connectivity.Finally, a single composite routing table is built at each node from thecollection of waveform routing tables.

It is possible to construct a variety of composite routing tablesdepending upon what routing criteria or combination of criteria arebeing optimized. Possible routing criteria to be optimized includecombinations of the following:

minimum number of hops;

minimum end-to-end latency;

maximum data throughput;

congestion avoidance;

minimum power consumption;

highest reliability, i.e., fewest dropped packets; and

minimum bandwidth used.

This system and method could be expensive in terms of both the OTA (overthe air) bandwidth consumed, and computationally (which translates intoreduced battery lifetime, increased memory usage, and increasedprocessor time usage).

It is possible to use a single OLSR process that reduces both bandwidthand computational expense.

Instead of running a parallel OLSR process in each node for eachwaveform, a single OLSR process is run in each node. This single OLSRprocess is modified to exchange a separate and independent set of1-hop-neighbor HELLO messages for each waveform. The HELLO messageexchanges 1-hop neighborhood information for that waveform. Each nodecan build a 2-hop neighborhood for each waveform.

The OLSR state table is extended to segregate link state information foreach of the 1-hop neighbors by waveform. Each node's 1-hop neighborhoodfor each waveform is distributed in a single transmit control message.This provides each node the information it requires to build its networktopology model of connectivity for each waveform. From thismulti-waveform network topology, each node builds its own compositeroute table.

This improvement merges the multiple OLSR processes into a single OLSRprocess, while keeping independent HELLO messaging for each waveform.Instead of each MPR transmitting separate TC messages for each waveform,every waveform's link states are included in a single transmit controlmessage. Bandwidth consumed is significantly reduced, along with thecomputational and memory burdens of a separate OLSR process per waveformand processing of separate transmit control message streams for eachwaveform.

In another aspect of the present invention, it is possible to use awaveform connectivity inference such that OLSR messages are transmittedusing a “base” waveform. The base waveform may or may not be thelongest-range waveform. The base waveform will typically be one of thelonger-range waveforms because a shorter-range waveform may not reachall nodes reachable by longer-ranged waveforms. Record receptioncharacteristics can occur for each received OLSR packet on the basewaveform. It is possible to use heuristics based upon OLSR packetreception characteristics and previously characterized relative waveformperformance to predict each node's 1-hop neighborhood connectivity foreach non-base waveform.

Possible extensions and improvements include using non-HELLO messages tocollect link-state information and statistics. For example, in someradio network beacons, data and any other message sent can be used tocharacterize the link base upon the particular waveforms used totransmit the packet and dynamically improve or adapt the heuristic usedto predict conductivity for other waveforms.

A good condition for the heuristic used to predict each waveform's 1-hopneighbourhood/connectivity is the received signal-to-noise ratio, S/N.Additional link parameter information such as fading and delay spreadand/or laboratory and field measurements can be collected and used. Itmay be useful to supplement the OLSR traffic reception parameterinformation with that of data traffic and other control traffic. It mayalso be useful to transmit some amount of “extra” OLSR traffic toestimate correct reception for other waveforms sufficiently well to beable to correctly populate each waveform's 2-hop neighbourhood. This alldepends on the particulars of the waveforms.

From this point onward, the process is similar to that of the singleOLSR process described above, except that in the waveform connectivityinference, predicted instead of measured 1-hop neighborhoods are usedfor all but the base waveform. MPR link-state and connectivity for eachwaveform is distributed in a single topology control message. Thisprovides each node the information it requires to build its networktopology model of connectivity for each waveform. From thismulti-waveform network topology, each node builds its own compositeroute table.

An alternate approach is to apply the heuristic (perform thelink-reception-characteristics-to-1-hop-neighbor translation) afterreceiving each MPR's topology control message instead of before an MPR'stopology control message is generated. Essentially, this pushesapplication of the heuristic from the source of the topology controlmessage to the destination of the topology control message. It alsomeans the reception characteristics of each received OLSR packet must becollected on a per-1-hop-neighbor basis and distributed in topologycontrol messages. Overall, it is probably simplest to apply theheuristic at the source.

The system is operable by approximately predicting each non-basewaveform's 1-hop connectivity, i.e., the probability that a transmissionwill be successfully received, given the 1-hop connectivity andreception characteristics of the base waveform. A signal-to-noise basedheuristic may accomplish this inference, but other heuristics that workcan be used.

In one non-limiting aspect, a waveform connectivity inference is animprovement over single OLSR process and multiple OLSR processessolutions. A waveform connectivity inference typically transmits thesame number of OTA OLSR packets as does traditional OLSR because it isusing only a single base waveform. It is also possible to sample somesubset of the waveforms beyond just the base waveform. It provides aspectrum of alternatives ranging from sampling such as the HELLOmessages only on the base waveform and up to sampling all the waveforms.For example, it is possible depending upon the details of the particularwaveforms involved, that sampling could occur for a few of the waveformsbecause of the particular relationship between the waveforms and predictthe remaining waveforms.

Multiple OLSR processes, on the other hand, transmit a separate set ofHELLO and topology control messages for each waveform to be supported.For example, a single OLSR process transmits a separate set of HELLOmessages for each waveform to be supported. This partially multipliesthe number of OLSR HELLO and transmit control OTA packets by the numberof waveforms supported for a single OLSR process and multiple OLSRprocesses. The large decrease in channel bandwidth used by the waveformconnectivity inference is a significant benefit as compared to thebandwidth used by multiple OLSR processes or a single OLSR processsampling all waveforms using HELLO messages. A waveform connectivityinference leaves more channel bandwidth to transport user data, ascompared to a multiple OLSR processes and a single OLSR process.

Waveform Connectivity Inference topology control messages contain moreinformation than standard messages. A waveform connectivity inferencetopology control message contains, in addition to the source node's basewaveform's MPR selector set, either a separate MPR selector set for eachadditional waveform or the reception characteristics for each MPRselector set link for each waveform. The waveform connectivity inferencetopology control message payload may overflow the link and/or PHY MTU(maximum transmission unit), thus necessitating transmission of a secondOTA packet to complete the waveform connectivity inference OTA message.When and whether this happens will depend upon both the MTU of thelink/PHY and the size of the network. The size of the network comes intoplay because topology control messages are flooded and multiple messagesmay be forwarded together in a single OTA packet.

OLSR typically transmits OTA HELLO messages every two seconds and OTAtopology control messages every five seconds. When a HELLO OTA messagetransmit time coincides with a topology control OTA message transmittime, the two messages can be placed into a single OTA packet, providedthere is no overflow of the link and/or PHY MTU. Likewise, the multipleOTA topology control messages originally generated by different multipleOLSR processes can be merged into a single OTA packet when they areforwarded during flooding. This somewhat mitigates the proliferation ofOTA messages generated by a single OLSR process and multiple OLSRprocesses.

A single OLSR process and multiple OLSR processes, however, transmit aseparate OTA HELLO message packet for each waveform so that therecipient can collect the packet's reception characteristics for thatwaveform—they must explicitly sample every waveform. The waveformconnectivity inference solution, on the other hand, explicitly samplesonly a single or small number of waveforms. Thus, the waveformconnectivity inference solution will transmit substantially fewer OTAmessages than a single OLSR process and multiple OLSR processes.

Since the heuristic, of necessity, makes its predictions based onincomplete input data, its predictions will generally include somedegree of error. Because routing errors are expensive (from the user'spoint of view), it is sensible to use a conservative heuristic to have ahigh degree of confidence that when the heuristic predicts a symmetricconnection exists, that the symmetric connection does, in fact, exist.In some examples, the system may fail to predict symmetric links whenthey do, in fact, exist. The better the heuristic, the more this“conservatism” cost can be minimized, but it will always be present tosome degree.

The amount of memory required for the single OLSR process, multiple OLSRprocesses, and waveform connectivity inference solutions is greater thanthat required by traditional OLSR using only a single waveform. This isdue to the necessity of including either a 1-hop neighborhood per nodeper waveform, or 1-hop reception characteristics per node per waveform,in each node's OLSR state table. Additional memory and cycles are usedin the construction of a two-dimensional network connectivity topologytable where the waveform is the second dimension instead of theone-dimensional network connectivity topology table maintained by atraditional OLSR.

It should be understood that the single OLSR process, multiple OLSRprocesses, and waveform connectivity inference approaches can be appliedto any link-state-based routing algorithm. It is more generallyapplicable than just OLSR.

Having the full connectivity matrix, for each waveform range available,facilitates optimizing the composite routing table based upon multiplecriteria. The idea of constructing a composite routing table frommultiple connectivity matrices (one for each waveform) may be novel.

In addition, it may be desirable to construct and maintain multipledifferent composite routing tables for different purposes and/ordifferent kinds of traffic, e.g., one composite routing table for QoS(quality of service) traffic, minimizing end-to-end latency givenvarious other constraints, such as a specified throughput andreliability. Another composite routing table can be optimized forminimum power consumption for best-effort traffic. Optimizing additionalcomposite routing tables for other criteria is also possible.

Standard OLSR only uses link state information gathered via HELLOmessages, i.e., OLSR's neighborhood probing control messaging intendedto assess link state. Every time a transmission-reception event occurs,such as transmission of data, beacon, OLSR control messages or other OTApackets, the opportunity to collect link state quality information forthe transmission waveform exists. Rather than just ignoring ordiscarding the link information from these non-OLSR-HELLO receptions,link characteristics for every reception should be collected. Likewise,the fact that a particular transmission failed to be received is alsouseful information characterizing a link and should be incorporated intothe heuristic. When the base waveform is used for transmission, thereception characteristics are used to augment the link state assessmentprovided by OLSR HELLO messaging.

In the case of a waveform connectivity inference, the measured linkcharacteristics at the receiver for transmissions using non-basewaveforms can be used in two different ways. First, they can be used toprovide a measured assessment of link quality to augment the linkquality predicted by the heuristic and be distributed in transmitcontrol messages. Second, when measured non-base waveform connectivitydiffers from predicted connectivity, the measured connectivity can beused to dynamically calibrate the prediction heuristic.

For a variety of reasons, non-base-waveform connectivity predicted bythe heuristic may be in error to a greater or lesser degree. Moreover,the optimal heuristic may not be static. It may change over time.

To improve non-base-waveform predictions, i.e., tune the heuristic, andto minimize the waveform connectivity inference “conservatism” cost asdescribed above, the link characteristics of non-OLSR transmissions canbe collected and used to provide feedback to the heuristic. For example,non-base-waveform receptions can be compared against the receptionpredicted by the heuristic and used to tune the heuristic to improvefuture predictions. This might be described as a “passive collection” ofheuristic-tuning data. Non-base waveform data can be collected when anon-base waveform is used for a transmission.

Another approach intentionally varies the transmission waveform used,among the non-base waveform set, to maximize the amount of useful,heuristic-tuning data collected. This might be described as “activecollection” of, or “probing” for, heuristic-tuning data. Essentially,the system actively probes the local 1-hop connectivity among non-basewaveforms in order to improve the performance of the heuristic. Data istransmitted that needs to be transmitted anyway. The waveform used forthese transmissions is varied to maximize the amount ofheuristic-improving information collected. Thus, little bandwidth usagecost is involved.

Typically, there would be little bandwidth cost involved except if alower-speed waveform is used to probe. It will take more channel time totransmit the OTA packet at the lower data rate, and thus, more bandwidthis used. If probing is used, the use of the higher-data-rate,shorter-range waveform imparts a greater probability that the packetwill be received incorrectly, as compared to using a lower-data-ratelonger-range waveform. Thus, the system may suffer the cost of eitherdropping the packet, for best-effort type of service, or having toretransmit the packet for reliable service, and therefore, end up usingmore channel time, and thus more bandwidth.

A waveform connectivity inference extends the standard OLSR routingalgorithm to handle multiple waveforms, each having differentradio-range characteristics, to produce a two-dimensional routing tableacross the dimensions of MAC destination address and waveform. It doesthis with minimal increase in channel bandwidth use.

The ability to generate full routing tables and next-hop relay tableswith little additional bandwidth usage when a plurality ofdifferent-ranged waveforms is in use is a significant advantage for anywireless mesh ad-hoc network.

Each option extends the standard OLSR (or other link-state) routingalgorithm to handle routing when multiple waveforms having differentradio-range characteristics are available. The system has the ability tobuild separate routing tables for multiple different-ranged radiowaveforms, and a single composite routing table based upon multipleoptimization criteria, and in the case of a waveform connectivityinference system, to do so in a channel-bandwidth-efficient fashion.

FIG. 10 illustrates a flowchart showing the multiple OLSR processes.Each OLSR process can perform its own independent set of HELLO messagetransmission using a different waveform. Each OLSR process can floodeither a single (periodic) topology control message for each waveform.Alternately, each OLSR process can flood a single (periodic) topologycontrol message containing topology information for all waveforms. Thelatter is more bandwidth efficient and thus is to be preferred. As shownin block 200, each OLSR process builds a model of network conductivitybased on a range of waveforms in the usual OLSR fashion.

Each OLSR process constructs a routing table for its waveformconnectivity (block 202). A composite routing table is built from thecollection of individual waveform routing tables based on routingcriteria such as the minimum number of hops; minimum end-to-end latency;maximum data throughput; congestion avoidance; minimum powerconsumption; highest reliability (fewest dropped packets) and minimumbandwidth used (block 204).

FIG. 11 shows a single OLSR process. Instead of running a parallel OLSRprocess in each wireless network node, only a single OLSR process is runin each node.

As shown at block 220, each node builds a 1-hop and 2-hop neighborhoodfor each waveform. The OLSR state table is extended to segregate linkstate information for each one-hop neighbor by waveform (block 222).Each MPR's selector set for each waveform is flooded in a single(periodic) transmit control message (block 224). Each receiving nodethen builds its own composite route table (block 226).

FIG. 12 shows the waveform conductivity inference process. As shown atblock 230, the reception characteristics of each received OLSR packetare recorded for the base waveform. A heuristic is used based upon OLSRpacket reception characteristics and the previously characterizedrelative waveform performance to predict each node's one-hopneighborhood connectivity for each non-base waveform (block 232). Theprocess continues similar to a single OLSR process (block 234).

Many modifications and other embodiments of the invention will come tothe mind of one skilled in the art having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is understood that the invention is not to be limited tothe specific embodiments disclosed, and that modifications andembodiments are intended to be included within the scope of the appendedclaims.

1-27. (canceled)
 28. A communications system, comprising: a plurality ofmobile nodes forming a mesh network; a plurality of wirelesscommunication links connecting the mobile nodes together; each mobilenode comprising a communications device and operative for transmittingdata packets wirelessly to other mobile nodes via the wirelesscommunications link from a source mobile node through intermediateneighboring mobile nodes to a destination mobile node using a link staterouting protocol and multiple waveforms, wherein each node is operativefor predicting 1-hop neighboring connectivity using heuristics based onreception characteristics for a received packet on a base waveform thatis chosen from the multiple waveforms wherein at least one of themultiple waveforms has a different range, transmission distance or reachthat is greater than the other multiple waveforms resulting in differentconnectivity.
 29. The communications system according to claim 28,wherein each mobile node is operative using multiple link state routingprocesses operating in parallel at a mobile node for each waveform. 30.The communications system according to claim 29, wherein each mobilenode is operative for transmitting and receiving separate HELLO andtopology control messages per waveform.
 31. The communications systemaccording to claim 28, and further comprising a network connectivitymodel at each mobile node for each waveform.
 32. The communicationssystem according to claim 31, and further comprising a routing table ateach mobile node that defines wireless routes for multiple networkconnectivity models based on routing criteria.
 33. The communicationssystem according to claim 32, wherein said routing criteria comprisesone or more of at least a minimum number of hops, minimum end-to-endlatency, maximum data throughput, congestion avoidance, minimum powerconsumption, a minimum bandwidth and dropped packets per route.
 34. Thecommunications system according to claim 28, wherein each mobile node isoperative using a single link state routing process for all waveforms bytransmitting separate HELLO messages to 1-hop neighbors and flooding onetopology control message per waveform.
 35. The communications systemaccording to claim 34, and further comprising a routing table at eachnode that segregates link state information for each 1-hop neighbor bywaveform.
 36. The communications system according to claim 28, whereinsaid reception characteristics comprise a received signal-to-noiseratio.
 37. The communications system according to claim 28, wherein saidlink state routing protocol, comprises an Optimized Link State Routing(OLSR) protocol.
 38. The communications system according to claim 28,wherein the multiple waveforms have different ranges.
 39. Acommunications system, comprising: a plurality of wireless nodes forminga mesh network; a plurality of wireless communication links connectingthe mobile nodes together; each wireless node comprising acommunications device and operative for transmitting data packetswirelessly to other nodes via the wireless communications link from asource mobile node through intermediate neighboring mobile nodes to adestination mobile node using a link state routing protocol and a basewaveform that is chosen from multiple waveforms wherein at least one ofthe multiple waveforms has a different range, transmission distance orreach that is greater than the other multiple waveforms resulting indifferent connectivity by predicting 1-hop neighborhood connectivitybased on a heuristic regarding packet reception characteristics andwaveform performance.
 40. A communications system according to claim 39,wherein a 1-hop neighborhood connectivity is predicted for each non-basewaveform.
 41. A communications system according to claim 39, whereineach 1-hop neighborhood for each waveform of a mobile node isdistributed via a single topology control message.
 42. Thecommunications system according to claim 39, and further comprising anetwork connectivity model at each mobile node for each waveform. 43.The communications system according to claim 42, and further comprisinga routing table at each mobile node defined by network connectivitymodels.
 44. The communications system according to claim 39, whereinsaid link state routing protocol comprises an Optimized Link StateRouting (OLSR) protocol.
 45. A method for communicating, comprising:forming a mesh network from a plurality of mobile nodes; transmitting adata packet across the mesh network from a source mobile node throughintermediate neighboring mobile nodes to a destination mobile node usinga link state routing protocol and multiple waveforms; and predicting1-hop neighboring connectivity using heuristics based on receptioncharacteristics for a received packet on a base waveform that is chosenfrom the multiple waveforms wherein at least one of the multiplewaveforms has a different range, transmission distance or reach that isgreater than the other multiple waveforms resulting in differentconnectivity.
 46. The method according to claim 45, which furthercomprises using multiple link state routing processes operating inparallel at a mobile node for each waveform.
 47. The method according toclaim 45, which further comprises transmitting separate HELLO andtopology control messages per waveform.
 48. The method according toclaim 45, which further comprises building a network connectivity modelat each mobile node.
 49. The method according to claim 48, which furthercomprises building a routing table at each mobile node that defineswireless routes for multiple network connectivity models based onrouting criteria.
 50. The method according to claim 45, which furthercomprises transmitting separate HELLO messages to 1-hop neighbors andflooding one topology control message per waveform.
 51. The methodaccording to claim 45, which further comprises predicting 1-hopneighborhood connectivity based on heuristics regarding packet receptioncharacteristics and waveform performance.
 52. The method according toclaim 45, which further comprises distributing each 1-hop neighborhoodfor each waveform via a single topology control message.